I would add that you consider distance, focus, size of image and offset from dead on center to the screen. All the under $200 projectors only have a vertical keystone adjustment. They do this by tilting a Fresnel (pron. Freh- NELL) lens that sits in between the LCD and the projection lens. This is a flat piece of plastic like those bookmark magnifiers. Concentric circles cut to refract the light. It bends the light to channel it into the projector lens. When you tilt it, it makes the image into a trapezoid. It gives you about 15 degrees of adjustment at the expense of sharpness in the plane of adjustment.
So in simple english, if you turn the projector on its side and move the projector to the side of the doorway to hid it and move the hotspot away from the eyes of the viewer, you will be able to correct the skew of the image to a maximum of 15 degrees as measured from the angle beteen the projector if it was pointed strait and the center of where you are actually pointing. That should work for you, in my opinion. But try to keep the projector on a tripod or other raised surface level with the center of the doorway since you can't correct for that keystoning.
Just FYI, many expensive projectors adjust the actual image and can correct a larger range and keystone in both the vertical and horizontal axis.
Next is throw distance and image size. Without a zoom lens, your only control of image size is moving the projector closer or farther to the door. So you need to make sure that sweet spot is available in your room or that you can move furniture
And lastly, you need to make sure the projector can focus at that distamce, which shouldn't be a problem in the range of a small window to a 120" screen (diagonally measured)
I have tested the Fixeover projector for around $185 and am very satisfied with it. I use 5 projectors in my display, 2 brand name used projectors, 2 cheap projectors and this one. This one does 720p native and downconverts 1080p. If the hallway is relatively dark and the light in the room behind sthe screen is dim but still reading light bright, it will be stunning.
Here is my opinion/recommendation:
Fixeover GP100 1280x800 resolution. Many clone units out there (Goodee, Tenker, CiBest, etc) around $190.
Epson VS240 800x600 native, but don't scoff at that, especially for a moving image. It is better than DVD quality, SVGA. 3 LCD chips! One for each color, red, greed and blue. 3000 true lumens. I haven't looked at the difference between that and the VS250 other than price, but this is the next step up for haunters.
Something interesting are the new DLP minis. They have a full Android OS, can download apps, have wifi and bluetooth... they are more like laptop projectors. Lots of possibilities with something like this such as streaming from youtube or a media server in your house. Look at the Wowoto H8 for $399. Same as Optoma Intelligo-S1which is a brand name (but a lot more). The iCodis CB300W is $5 less than the wowoto and also the same guts.
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